Topic: Vapor lock???

1971 van with stock style fuel pump and PICT 34 carb.

Finishing an engine rebuild but can't keep it running.  Doesn't idle and seems like it runs out of gas.  "Bubbles" appear in the in-line fuel filter so I suspect a vapor lock. The fuel filter has very little fuel in it once it is running.

The fuel pump is new, the lines are new, the gas tank was cleaned out, no gas leaks, the gas seems clean.

The fuel line is running from the fuel pump, through the fan housing, through the firewall to the tank.

I suspect that the line should NOT run through the fan housing and instead just wind its way up pass the coil and then down through the firewall to the tank.  Is this correct route?  Does it sound like a vapor lock problem?


Thanks so much.

Re: Vapor lock???

Toviro: On Type 1 engines (which came stock on the 1971 Bus; is that what yours has?) the accelerator cable should be the thing running through the fan shroud....could someone have accidentally used this passage to run a fuel line?? Bottom line is that the fuel line should be routed as far away from hot engine parts (exhaust manifold, cylinder heads, etc.) as possible. Where is your inline filter located? Between pump and carb or before the carb? A few random bubbles may be noticed if it's in the former location. As noted in another thread, fuel level in a perfectly functioning fuel filter can range from almost empty to almost full.

Vapor lock usually occurs when an engine is hot, or the weather is hot, and fuel "boils" out of the metal gas lines or out of the carb bowl, or out of the fuel pump. The fuel pump can pump liquid gasoline but can't pump a vapor. This can lead to hard starting and in certain conditions can cause the engine to simply stall while running. Poor idling sounds like a carb adjustment issue.  How is your timing? Does the engine seem to run hot or have you even been able to get it to run long enough to get hot?

I'd focus on the carb and the timing.

Clancy

Re: Vapor lock???

Did you put a additive in the gas, such as a carb cleaner, additives can make gas go into a vapor easier, causing vapor lock on a car that has not had the problem before.

Deron.

Re: Vapor lock???

The metal gas line was routed through the fan housing in a hole in line with the hole in the firewall.  Rerouted outside and around the fan housing.  Problem seems fixed.

Thanks so much for all your help.

Now on to trying to figure out how to tune the carb and time it so it runs good.

Re: Vapor lock???

Toviro: So your accelerator cable was through its own separate hole in the fan? The one with a metal tube that protects the cable as it passes through the shroud? Can you describe approximately where the fuel line passed through the shroud?

What kind of distributor are you running with your 34 PICT? This is an important consideration.  Timing is pretty straight forward if you have some good directions. Take a look at http://www.vw-resource.com/tune-up.html Do you have a good manual to guide you? Also take a look at the procedures to adjust your valves: http://www.vw-resource.com/valveadj.html

Lots of curiosity questions, but I'm glad that you have apparently solved the "vapor lock" problem.

Clancy

Re: Vapor lock???

Clancy:  The hole is about 5 o'clock and about 30mm from the hose hook-up on the fan housing, almost directly below the lower mounting screw for the coil.  Goes straight through the housing then winds around the shroud below the oil cooler and through the fire wall.

Running a 009 distributor and reading alot about compatibility problems on this and other web sites.  I am tuning the 009 to 30 degrees at 3000 Rpm, which seems about 8.5 at idle.   I have been using the info on the web sites you mentioned with many thanks to those folks for their good information.

Using an old copy of Muir and the Bentley books with some success and a lot of head scratching.

Thanks so much for all your help.

Re: Vapor lock???

Here's how the line "should" be routed.  It's not the best photo but you can see the rubber line from the frame, the copper line through the front tin and routed along the side of the fan housing (clipped to the side mounting bolt), and then into the engine compartment behind and above the manifold.  Ignore the yellow wire.
http://www.geocities.com/dyouse2000/VWphotos/059.jpg

David H
'66 VW Beetle w/sunroof
http://tinyurl.com/qhw59
"Where am I going ... and why am I in this handbasket?"

Re: Vapor lock???

David,

Nice picture of your engine...looks clean enough to eat off of.

Concerning the fuel line...I saw in the picture what looks like a "clear" see-thru line (just above the front most part of the heater box.  Is that correct...if so is it gasoline resistant?

I haven't seen copper tubing used as fuel line before.  Is it gasoline resistant?

- Nick

1979 Super Beetle Convertible

Re: Vapor lock???

Very observant.  The clear line you see isn't part of the finished product.  It was just a temporary add-in to stick in a gas can to supply gas to the engine for test running.  The "copper" line isn't really copper; it's steel but had some kind of coating on it that made it look almost like copper.  It's the original stock fuel line.

David H
'66 VW Beetle w/sunroof
http://tinyurl.com/qhw59
"Where am I going ... and why am I in this handbasket?"

Re: Vapor lock???

Thanks for clarifying that the line is coated steel, not pure copper. Copper tubing is tempting and easy to use, but work hardens in a high-vibration installation (as on engines) so that it may eventually crack and break. Not a good idea.

Re: Vapor lock???

hi i am in the middle of a restoration...
i had problem to find some fuel line here in place where i live..

i can find only iron lines and copper lines...
the iron lines are very hard to work and bend them to pass through chassis tunel..
in the other hand copper will make corrosion if join with iron steel...

what are you suggesting me?

if make a protection of copper line so dont get touch with iron is good solution??